1. Field of the Invention
This document relates to an impulsive driving liquid crystal display device and a driving method thereof.
2. Discussion of the Related Art
An active matrix driving liquid crystal display device displays a moving image using thin film transistors (TFTs) as switching elements. Since the liquid crystal display device can be formed into a small size compared to a cathode ray tube (CRT), it is applied to a television set as well as a display device in a portable information device, an office machine, a computer, etc., and gradually replaces the CRT.
The liquid crystal display device has a motion blur phenomenon in which a picture of a moving image is blurred due to retention characteristics of the liquid crystal. As shown in FIG. 1, the CRT displays an image in an impulsive driving method, in which light is emitted from a fluorescent material for a very short time to display data in a cell and then light is not emitted from the cell any more. Compared to this, as shown in FIG. 2, the liquid crystal display device displays an image in a hold-type driving method, in which data is supplied to a liquid crystal cell during a scanning period and then the data charged in the liquid crystal cell is maintained for the remaining field period (or frame period).
Since the moving image displayed on the CRT is driven in the impulsive driving method, the image perceived by a viewer becomes clear as shown in FIG. 3. On the contrary, as shown in FIG. 4, in the moving image displayed on the liquid crystal display device, the image perceived by the viewer is blurred due to the retention characteristics of the liquid crystal. The difference of images perceived the CRT and the liquid crystal display device results from an integration effect of the image that continues temporarily in the viewer's eyes that follow the movement. Accordingly, even though a response speed of the liquid crystal display device is high, the viewer sees a blurred image by discordance between the movement of eyes and a static image for each frame. In order to improve the motion blur phenomenon, the impulsive driving method that drives the liquid crystal display device by inserting black data on a screen after displaying video data on the screen, i.e., a black data insertion (BDI) method is proposed. For example, as shown in FIG. 5, according to the black data insertion method, a screen is divided into three blocks, a video data voltage is sequentially charged by each line in one block A1 of the divided blocks, and a black voltage is simultaneously charged by continuous four lines in another block A2. In the this manner, the black data insertion method accomplishes an impulsive driving effect by sequentially charging video data lines one by one in the respective blocks A1 to A3 and then sequentially charging a black voltage by four lines. In order to simultaneously select the lines in which the black voltage is charged, a gate drive IC simultaneously applies gate pulses to adjacent gate lines.
However, the impulsive driving method needs many line memories because it is necessary to make a driving frequency of the liquid crystal display device high and to store a large quantity of data for many lines. Furthermore, it is necessary to make a logic circuit and a control algorithm of a timing controller complicated.